1. Field of the Invention
The present invention pertains to coupling apparatus for joining elongated members such as conduits or pipes. Specifically, it pertains to coupling apparatus suitable for connecting nonaligned pipes and conduits such as may be frequently necessary in submarine installations.
2. Description of the Prior Art
Many coupling devices have been developed for joining the ends of two conduits or for coupling a conduit to some other apparatus. One general type of a coupling device is sometimes referred to as a ball and socket joint or coupling, in which the ball (male) member is attached to one conduit and the socket (female) member to another. The male member is received within the female member and some means is provided for holding the two members together.
In recent years, couplings of the ball and socket type have been developed for submarine installations. Some of these couplings have been used for providing a flexible joint for connecting a marine riser or conduit to a submarine wellhead so as to provide communication between the submarine wellhead and a drill ship or the like. With these couplings, a ball member may be latched into the socket member by a radially deformable collar which is contracted to the holding position by an annular piston or some other similar device. Such flexible couplings permit limited relative rotary and bending movement between the coupled conduits. For submarine wellhead and riser type installations, this is desirable. Such flexible ball and socket couplings may be seen in U.S. Pat. Nos. 3,333,870; 3,450,421; and 3,695,633.
The flexible coupling designs for wellhead riser installations are not necessarily suitable for connecting pipe sections of a high pressure circulating fluid pipeline which may lie for prolonged periods on the sea floor. Although ball and socket couplings may be useful for connecting sections of such a pipeline which very frequently are not coaxially aligned, it is necessary to provide some sort of locking or gripping system which grips the ball with sufficient force to prevent it from turning or swiveling in the joint. In this manner, the connected conduits become a fixed unit with good mechanical continuity capable of withstanding the strong forces and stresses existing in pipelines.
Ball and joint couplings are now being developed, similar to ball and joint submarine wellhead/riser couplings, for connecting sections of submarine pipelines. One such connector may be seen in U.S. Pat. No. 3,874,706. However, like in most submarine wellhead/riser couplings, this coupling utilizes hydraulic mechanisms and it is necessary to use a pressurized fluid to actuate the locking mechanism. While such couplings are useful for installations situated near a platform which supports a central hydraulic system to feed the hydraulic mechanisms, they are poorly adapted for fitting in a pipeline at points that may be inaccessible to a central hydraulic system. Furthermore, in a pipeline application, the ball and socket joint must be rigidly maintained by maintaining hydraulic pressure thereon or by using a fluid, such as polymerizable resin, which hardens within the coupling so as to keep it fixed in the locked position. Such a method of fixing the locking system, as the latter, has the disadvantage of being irreversible, preventing uncoupling and replacement of malfunctioning components.
In a more recently developed coupling, shown in U.S. Pat. No. 4,040,650, a purely mechanical worm and worm wheel locking mechanism is provided instead of hydraulic type mechanisms. The worm and worm wheel arrangement allows the coupling to be reversible, i.e. it may be coupled and uncoupled with the same ease. It also allows the coupling to be operated with a substantial mechanical advantage. The inherent self-locking design of worm and worm wheel arrangements makes the coupling autonomous, operable at almost any location and capable of being left in its locked position without having to maintain any applied force thereon. Thus, it is more suitable for connecting conduits in a pipeline than hydraulically operated ball and socket couplings.
In both of the hydraulically or mechanically operated ball and socket couplings of the prior art, the means for gripping the ball usually includes metallic gripping elements which are radially movable from an outward position, in which the ball is freely permitted to enter and exit the socket, to inward positions firmly and rigidly gripping the ball and locking the ball and socket in a fixed articulated relationship. The mounting of the gripping elements is somewhat complicated, particularly mounting them in such a way as to ensure opening or return to the outward position for allowing removal of the ball. Furthermore, in most of the prior art ball and socket couplings suitable for pipeline use, including those just discussed, some sort of axially movable sleeve cam member is provided for camming or forcing the gripping elements into gripping contact with the ball member. Such sleeve members of the prior art generally move in an axial direction toward the conduit to which the ball member is attached. This means that the components of the force applied to the gripping elements includes at least some force component which is tending to force the ball member axially out of the socket. This force, through it be small, may be sufficient to prevent the coupling from being rigidly locked in the necessary articulated relationship. Furthermore, this force may be sufficient to prevent maintenance of the necessary sealing forces on the annular seal which is normally provided between the ball member and the socket member. This is particularly true if there is any axial play or slack present in the machined parts associated with the gripping assembly of the coupling.